In-line heat-exchanger and method of forming same

ABSTRACT

An in-line heat exchanger comprising first and second lengths of seamless, walled tubing, the first length of tubing characterized by a larger diameter than the diameter of the second length of tubing, and the second length of walled tubing disposed within the first length of walled tubing. A plurality of longitudinally-extending channels are defined in the wall of at least one of the first and second lengths of tubing, the channels defining therebetween a plurality of longitudinally-extending passageways in the area between the walls of the first and second lengths of tubing. Terminal portions provided at opposite ends of the first length of tubing are each sealed with respect to the second length of tubing, each terminal portion defining one of an inlet or an outlet, and each terminal portion defining at least one interior passageway between the terminal portion and the wall of the second length of tubing, the at least one interior passageway communicating the plurality of longitudinally-extending passageways with one of the inlet or outlet.

FIELD OF THE INVENTION

The present invention relates to tube-in-tube style, in-line heat exchangers and their manufacture.

BACKGROUND

Conventional refrigeration systems continuously circulate refrigerant in an evaporator and a condenser in a closed system such as shown in the simplified diagram of FIG. 1. These systems have a high-pressure side (indicated by the thin lines 2) and a low-pressure side (indicated by the thick lines 3). Beginning at the inlet to evaporator 1 and moving counter-clockwise in the direction of the arrows, a supply of low-pressure refrigerant liquid expands, absorbs heat, and evaporates, changing to a low-pressure, saturated, dry gas. A compressor 4 draws this gas from the evaporator 1 through a suction line (3). Compressor 4 increases the pressure of the gas, and discharges the high-pressure and high-temperature refrigerant gas to a condenser 5 through a discharge line. Heat is removed from the gas at the condenser 5, which gas then condenses and becomes a high-pressure liquid. The high-pressure refrigerant liquid flows from the condenser 5 into a receiver tank 6. From the receiver 6 the high-pressure refrigerant liquid flows toward the evaporator 1 in a pipe called the liquid line. In order for the refrigerant liquid to evaporate and cool the fluid needing refrigeration, its pressure must be reduced. This pressure reduction is achieved by passing the high-pressure refrigerant liquid through a flow restrictor (also called an expansion device). One frequently employed flow restrictor is a thermal expansion valve 7, or “TXV,” positioned proximate the evaporator and operative to sense both the pressure in the evaporator and, via sensor 9 operatively connected (shown in dotted line) thereto, the temperature at the refrigerant vapor outlet of the evaporator. The flow of refrigerant into the evaporator 1 is controlled by the degree of superheat of the suction gas.

A heat exchanger 8 (depicted in dashed lines) between the liquid line and the suction line is also conventionally provided to facilitate cooling of the high-pressure and high-temperature liquid by moving it in close proximity to, and flowing oppositely of, the low-pressure and low-temperature gas drawn from the evaporator 1. Conventionally, heat exchangers comprise tubing made up of concentric inner and outer tubes. According to this construction, also referred to as a tube-in-tube style heat exchanger, the high-pressure, high-temperature liquid is caused to flow through the annular space between the inner and outer tubes, while evaporated low-pressure, low-temperature refrigerant gas is caused to flow through the inside of the inner tube of the heat exchanger. The high-pressure, high-temperature liquid and the low-pressure, low-temperature gas exchange heat through the inner tube, whereby the high-pressure, high-temperature liquid is cooled. This heat transfer process of the high-pressure and high-temperature liquid increases the sub-cooling thereof.

Conventional tube-in-tube style heat exchangers are, unfortunately, complex in construction and therefore costly to manufacture. Exemplary in these regards are the heat exchanger tubes disclosed in Usui, U.S. Pat. No. 7,044,210, and McLain, U.S. Pat. No. 3,831,675. It would therefore be desirable to have a tube-in-tube style heat exchanger that is easy and inexpensive to manufacture, and which allows efficient heat transfer between the inner and outer tubes thereof.

SUMMARY OF THE INVENTION

According to the specification, there is disclosed an in-line heat exchanger, comprising first and second lengths of seamless, walled tubing, the first length of tubing characterized by a larger diameter than the diameter of the second length of tubing, and the second length of walled tubing disposed within the first length of walled tubing. A plurality of longitudinally-extending channels defined in the wall of at least one of the first and second lengths of tubing, the channels defining therebetween a plurality of longitudinally-extending passageways in the area between the walls of the first and second lengths of tubing. Terminal portions provided at opposite ends of the first length of tubing are each sealed with respect to the second length of tubing, and each defines one of an inlet or an outlet. Each terminal portion further defines at least one interior passageway between the terminal portion and the wall of the second length of tubing, the at least one interior passageway communicating the plurality of longitudinally-extending passageways with one of the inlet or outlet.

In one embodiment, the terminal portions are each defined by opposite ends of the first length of tubing that are sealed against the wall of the second length of tubing. In another embodiment, the terminal portions comprise separate lengths of tubing that are connected to each of the first and second lengths of tubing.

According to one feature hereof, the terminal portions may have different longitudinal dimensions with respect to each other so as to define interior passageways of different volumes. Furthermore, one of the terminal portions may define an interior passageway capable of accommodating an amount of a high-pressure, sub-cooled fluid at least equivalent to the weight of the quantity of a high-pressure fluid that can be accommodated in the receiver dryer in a fully-charged air-conditioning system.

Per one aspect of the invention, the plurality of longitudinally-extending channels are defined in only the wall of the first length of tubing. However, the plurality of longitudinally-extending channels may, alternatively, be defined in the wall of only the second length of tubing, or in the walls of both of the first and second lengths of tubing.

According to another aspect of the invention, the plurality of longitudinally-extending channels comprise at least two discrete sets of longitudinally-extending channels. Each discrete set of channels may, moreover, be separated from the other by an intermediate space defined in the area between the walls of the first and second lengths of tubing. Per another feature of the invention, at least one such discrete set of channels may be offset relative to the one or more other sets of channels.

Per still another feature, the plurality of longitudinally-extending channels may each define a helical path.

The specification further discloses an exemplary method for forming such tube-in-tube style, in-line heat exchangers, the method comprising the steps of:

providing at least first and second lengths of seamless, walled tubing, the first length of tubing characterized by a larger diameter than the diameter of the second length of tubing, and each of the at least first and second lengths of walled tubing characterized by generally circular cross-sectional shapes;

inwardly deforming circumferentially spaced-apart portions of the wall of at least one of the first and second lengths of tubing to form along a longitudinal length thereof a plurality of longitudinally-extending channels; and

positioning the second length of walled tubing within the first length of walled tubing so that the walls of the first and second lengths of tubing are in contact proximate the plurality of longitudinally-extending channels, and so that, intermediate the areas of contact between the first and second lengths of walled tubing proximate the plurality of longitudinally-extending channels there are defined between the walls of the first and second lengths of tubing a plurality of longitudinally-extending passageways.

In another embodiment thereof, the method for forming in-line heat exchangers comprises the ordered steps of:

providing at least first and second lengths of seamless, walled tubing, the first length of tubing characterized by a larger diameter than the diameter of the second length of tubing, and each of the at least first and second lengths of walled tubing characterized by generally circular cross-sectional shapes;

positioning the second length of walled tubing within the first length of walled tubing; and

deforming inwardly circumferentially spaced-apart portions of the wall of the first length of tubing to bring the same into contact with the wall of the second length of tubing, thereby forming along a longitudinal length of the tubing a plurality of longitudinally-extending channels in the wall of the first length of tubing, the plurality of longitudinally-extending channels defining therebetween a plurality of longitudinally-extending passageways between the walls of the first and second lengths of tubing.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, which show exemplary embodiments of the present invention, and in which:

FIG. 1 is a simplified diagram of a conventional air-conditioning system;

FIG. 2A is a lateral elevational view of a heat exchanger in accordance with an exemplary embodiment of the invention;

FIG. 2B is a cross-sectional view of the heat exchanger of FIG. 2A;

FIG. 3 is a lateral elevational view of a heat exchanger in accordance with a second exemplary embodiment of the invention;

FIG. 4 is a simplified schematic depicting the heat exchanger of FIG. 3 in an exemplary operational environment;

FIG. 5 is a lateral elevational view of a heat exchanger in accordance with a third exemplary embodiment of the invention;

FIG. 6 is a lateral elevational view of a heat exchanger in accordance with a fourth exemplary embodiment of the invention;

FIG. 7 is a lateral elevational view of a heat exchanger in accordance with a fifth exemplary embodiment of the invention;

FIG. 8 is a cross-sectional view of a heat exchanger in accordance with an alternative construction;

FIG. 9 is a cross-sectional view of a heat exchanger in accordance with an alternative construction;

FIG. 10 is a perspective view of an exemplary forming apparatus for making heat exchangers in accordance with the present invention; and

FIGS. 11A and 11B are cross-sectional view of the press portion of the apparatus of FIG. 10, depicting the step of forming channels in the walled tubing comprising the heat exchanger.

DETAILED DESCRIPTION

As required, a detailed embodiment of the present invention is disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The accompanying drawings are not necessarily to scale, and some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

Referring now to the drawings, wherein like numerals refer to like or corresponding parts throughout the several views, the present invention is characterized, according to a first embodiment thereof, as a tube-in-tube style, in-line heat exchanger (identified generally at 10) comprising first 20 and second 30 lengths of walled tubing arranged with the second length 30 of tubing disposed within the inner diameter of the first length 20 of tubing. FIGS. 2A and 2B. While generally described herein in connection with air conditioning systems, it will be understood by those skilled in the art that the heat exchanger of the present invention may be incorporated in any system employing a two-phase refrigerant fluid.

As shown best in FIG. 2B, the second length 30 of tubing is characterized by a generally circular cross-section, with the area 31 defined by the inner diameter defining a passageway for the flow of a low-pressure, low-temperature fluid, such as a refrigerant gas, therethrough. The first length 20 of tubing is characterized by a corrugated or wavy cross-section defined by a plurality of circumferentially spaced-apart, longitudinally-extending channels 21. Proximate the nadir of each such channel 21, the inner surface of the wall of the outer, first length 20 of tubing is in contact with the exterior surface of the wall of the inner, second length 30 of tubing. Intermediate the channels 21 is defined in the annular space between the first 20 and second 30 lengths of tubing a plurality of longitudinally-extending passageways 40, each such passageway closed off from the other by reason of the contact between the interior of the wall of first length of tubing 20 and the exterior of the wall of the second length of tubing 30. Each passageway 40 defines an internal channel for the flow of a high-pressure fluid, such as a high-pressure liquid, therethrough in a direction opposite the direction of the low-pressure fluid flow through the inner diameter 31 of the second length of tubing 30.

Referring particularly to FIG. 2A, the heat exchanger according to the illustrated embodiment will, in order to be integrated in-line into a refrigeration system (such as depicted in schematically in FIG. 3) or other operational environment, include terminal portions 22 a, 22 b disposed exteriorly of, and sealed with respect to, the second length of tubing 30, as shown in FIG. 2A (where the second length of tubing 30 is shown in dashed lines). Each terminal portion 22 a, 22 b communicates a passageway 23 a, 23 b, respectively, defining one of an inlet or an outlet for a high-pressure fluid (such as for a high-pressure liquid in a vehicle air-conditioning system) with, respectively, at least one interior passageway 24 a or 24 b (such as, for instance, a circumferential space) defined in the area between the terminal portion and the wall of the second length of tubing 30. Where passageway 23 a defines the inlet, interior passageway 24 a communicates the high-pressure fluid from the inlet to the passageways 40, while the passageway 23 b communicates the high-pressure fluid exiting passageways 40 to the outlet defined (in this example) by the passageway 23 b.

As those skilled in the art will appreciate, the number of passageways 40 and their individual cross-sectional dimensions, as well as the dimensions of the inner diameter 31 of the second length of tubing 30, and the thickness of the walls of each of the first 20 and second 30 lengths of tubing will vary in accordance with the type of two-phase fluids employed in, and other known operating parameters of, the system. Generally speaking, however, it is contemplated that the number of passageways 40 and their individual cross-sectional dimensions will correspond to the cross-sectional dimensions of the interior passageways 24 a or 24 b defined in the area between the terminal portions 22 a, 22 b, respectively, and the exterior of the wall of the second length of tubing 30.

It will also be understood by those skilled in the art that the length of the active heat-transfer area—that is, the length of the portion of heat-exchanger 10 comprising channels 21 and corresponding passageways 40—will vary according to the particular parameters (e.g., air conditioner size and cooling load) of the system in which it is incorporated. Furthermore, while the heat exchanger 10 depicted in the several embodiments disclosed herein is straight, it will be understood that the tubing may be bent—typically along the length of the active heat transfer surface—as required to accommodate the physical limitations of the space in which the heat exchanger 10 is disposed, to make necessary connections between the opposite ends of the second length of tubing 30, etc. And, in practice, the heat exchanger as disclosed herein has demonstrated the ability to be bent in multiple locations without collapsing the passageways 40.

As depicted, the second length of tubing 30 extends beyond the terminal portions 22 a, 22 b. The length of these extensions will vary according to the particular application and, in any known manner, the opposite free ends of the second length 30 of tubing may be secured to upstream and downstream components in the system in which the heat-exchanger is employed.

With continuing reference to FIG. 2A, it is contemplated that the terminal portions 22 a, 22 b may, as shown, be formed from terminal sections of the first length of tubing 20 that are not formed with channels 21 (so that the high-pressure fluid can move freely from the inlet into each of the passageways 40 and, at the opposite end of each of these passageways 40, may likewise move freely to the outlet). This may be accomplished, for example, by crimping the ends 25 a, 25 b against the second length of tubing 30. The crimped ends 25 a, 25 b may be brazed or otherwise sealed by conventional means against the tubing 30 so that high-pressure fluid is able to move only between the inlet and outlets of terminal portions 22 a, 22 b.

Alternatively, it is contemplated that the terminal portions may comprise separate lengths of tubing that are connected to each of the first and second lengths of tubing.

While a variety of materials may be employed for the heat exchanger of the present invention, including for the first 20 and second 30 lengths of tubing, suitable exemplary materials include metals such as steel, stainless steel, aluminum, aluminum base, copper, copper base alloys and nickel and nickel base alloys.

Referring next to FIGS. 3 and 4, there is shown an alternative embodiment wherein the heat exchanger 10′ is characterized by terminal portions 22 a′, 22 b′ of dissimilar longitudinal dimensions. More particularly, the terminal portion at which the outlet is defined (22 b′ in the illustrated example) has relatively greater longitudinal dimensions than the terminal portion at which the inlet is defined (22 a′ in the example). The longitudinal dimension of terminal portion 22 b′ is such that the volume of the interior passageway 24 b′ defined in the area between the terminal portion 22 b′ and the exterior of the wall of the second length of tubing 30′ is capable of accommodating, by weight (e.g., in grams), an amount of high-pressure, high-temperature fluid at least equivalent to the weight (e.g., in grams) of the quantity of high-pressure, high-temperature fluid that can be accommodated in the receiver dryer (whether integrated with the condenser or of the stand-alone type) in a fully-charged vehicle air conditioning system. Referring specifically to FIG. 4, it will further be noted that the outlet to the thermal expansion valve 7 is oriented to provide gravity feed of sub-cooled, high-pressure fluid thereto. Such orientation in particular serves to reduce noise at the thermal expansion valve.

By the foregoing, the inventive heat exchanger provides a fluid storage capability and, moreover, the sub-cooled fluid metered to the thermal expansion valve 7 is characterized by a lower pressure drop than in conventional systems. This improves vehicle fuel economy (when employed in a vehicle air-conditioning system), increases the cooling capacity of the evaporator, and permits relocation or even removal of the receiver dryer or integrated receiver found in conventional vehicle air-conditioning systems.

While, according to the aforedescribed embodiments, the channels 21, 21′ (and corresponding passageways 40, 40′) are depicted as being continuous for the length of the active heat-transfer area, it will be understood that they may be alternatively configured. Thus, for instance, it is contemplated that, according to the embodiment of FIG. 5, heat exchanger 10″ may have formed therein a plurality of longitudinally discontinuous channels 21 a″, 21 b″ that are interrupted one or more times along the length of the tubing 20″ to define therebetween, and in the area between the first 20″ and second 30″ lengths of tubing, one or more intermediate spaces 41″ in which high-pressure, high-temperature fluid exiting the passageways 40 a″ would flow before entering further, downstream passageways 40 b″. It will be understood that such intermediate spaces 41″ beneficially facilitate mixing of the fluid flowing therein.

Alternatively, in another embodiment of the heat exchanger 10′″ (FIG. 6), the channels 21 a′″, 21 b′″, 21 c′″ are longitudinally discontinuous, being interrupted by one or more intermediate spaces 41 a′″, 41 b′″, with the successive set of channels 21 b′″, 21 c′″ (and, therefore, downstream passageways, e.g., 40 b′″, 40 c′″) being offset relative to each preceding set of channels 21 a′″, 21 b′″ (and, therefore, upstream passageways, e.g., 40 a′″, 40 b′″). As shown the intermediate spaces 41 a′″, 41 b′″ of this embodiment are of shorter longitudinal dimensions than those of the embodiment of FIG. 5. It will be appreciated that the length of such intermediate spaces may be varied as desired, subject only to the provision that fluid flowing through one set of upstream passageways be able to continue flowing into successive downstream passageways.

It will also be appreciated that any number of sets of such discontinuous channels, whether aligned or offset, may be provided, depending upon the length of the channels in such sets and the overall length of the heat exchanger.

According to a still further embodiment of the heat exchanger 10″″ of the present invention, shown in FIG. 7, the channels 21″″ may be formed so as to each define a helical path along the length of the first length of tubing 20″″ between the terminal portions 22 a″″, 22 b″″. Optionally, the heat exchanger 10″″ of this embodiment may be further characterized by longitudinally discontinuous channels, such as exemplified in foregoing embodiments, and one or more intermediate spaces (not shown) disposed therebetween.

While, in each of the aforedescribed embodiments, the plurality of longitudinally-extending channels 21, 21′, 21″, etc. are shown as being defined in the wall of the first length of tubing 20, 20′, 20″, etc., it is contemplated that these channels may, alternatively, be defined in the second length of tubing 30, 30′, 30″, etc., such as depicted in FIG. 8, or even on both lengths of tubing, such as shown in FIG. 9.

Referring next to FIGS. 10 through 11B, the exemplary method by which the heat exchangers as heretofore described may be manufactured will be better understood.

According to the illustrated embodiment, there is provided a forming apparatus (indicated generally at 100) essentially comprising an hydraulically-actuated press 101 and an hydraulically-actuated carriage assembly 120. Press 101 more particularly comprises a stationary, split-ring element 102 supporting a plurality of rollers 103 arranged circumferentially, and equidistant from each other, about a central opening 104 which, in operation of the apparatus, is occupied by one or both of the first 20 and second 30 lengths of tubing. The relative distance between each roller 103 corresponds to the dimensions of the plurality of passageways 40 to be formed in the tubing. While, in the illustrated embodiment, eight such rollers 103 are depicted, it will be understood that the number may be varied according to the desired number, and dimensions, of the channels 21 and corresponding passageways 40.

Rollers 103 are each disposed on support members 105 riding in, and reciprocally moveable with respect to, radial openings 106 defined in the ring element 102. As shown best in FIG. 9, each support member 105 has an angled cam-following surface 107 corresponding approximately in shape to the angled surface 108 of cam member 109. Cam member 109 defines a ring-like shape of greater diameter than the split-ring element 102. Cam member 109 is hydraulically reciprocally-moveable along an axis coaxial with the central axis of split-ring element 102 so as to selectively move the angled surface 108 thereof into and out of engagement with the co-acting, cam-following surfaces 107.

With reference particularly to FIG. 9, carriage assembly 120 comprises a mechanical grip 121, such as, for example, a chuck, in the opening 122 of which are fixedly retained first 20 and/or second 30 lengths of tubing. Mechanical grip 121 is secured to a sled 123 that rides, under power of an hydraulic piston 125, freely along rails 124.

Referring also to FIGS. 9A and 9B, there are provided in operation of the aforedescribed apparatus first 20 and second 30 lengths of cylindrical, walled tubing arranged with the second length of tubing 30 disposed within the first 20. The tubes 20, 30 so arranged are fixed in position within opening 122 of the mechanical grip 121 so that a length of the tubes 20, 30 extends from the grip 121 in the direction of the press 101. As noted, at this stage both the first 20 and second 30 lengths of tubing are characterized by generally circular cross-sections, as shown in FIG. 9A, the first length 20 having an inside diameter larger than the outer diameter of the second length 30 of tubing so that, when the lengths of tubing are arranged one within the other, an annular space is defined between the exterior and interior surfaces of the walls thereof.

Subsequently, the sled 123 is moved by operation of the piston 125 in the direction of the press 101 so as to position the tubing 20, 30 in the central opening 104. FIG. 9A. At the desired position along the length of the tubing 20, 30, and as the tubing is continually urged through the central opening 104 by corresponding movement of the sled 123, the cam member 109 is moved over the split-ring element 102 so as to bring the angled surface 108 into engagement with cam-following surfaces 107 of the support members 105. By the co-action of these surfaces 107, 108, each support member 105 is driven radially inward into its respective radial opening 106 until the rollers 103 are brought into contact with the exterior surface of the first length 20 of tubing to form the longitudinally-extending channels 21 heretofore described. More particularly, as the pressure applied by rollers 103 increases, the wall of the first length 20 of tubing is locally deformed in the area of each deforming member 60. FIG. 9B. The pressure applied by each roller 103 is sufficient to inwardly deform the wall of the first length 20 of tubing proximate thereto until the wall has been urged inwardly to the point where the interior surface thereof is in contact with the exterior surface of the wall of the second length 30 of tubing. As the tubing continues to be urged through the central opening 104 by corresponding movement of the sled 123, this deforming pressure continues, thus forming channels 21 (and the corresponding passageways 40) of lengths determined by the duration of operation of the forming apparatus.

The amount of deforming pressure applied will, naturally, vary with the material of the first 20 and second 30 lengths of tubing; however, the amount of deforming pressure will at least be sufficient to bring the interior surface of the wall of the first length 20 of tubing into contact with the exterior surface of the second length 30 of tubing so as to form the plurality of channels 21 and, correspondingly, the plurality of passageways 41 between the first and second lengths of tubing.

It will be appreciated that, by the foregoing method of construction, the inventive heat exchangers may be fashioned from seamless tubing, rather than being formed from sheets of material that are first formed to include the plurality of channels and then joined end-to-end to define tubular shapes.

According to the aforedescribed methodology, it will be appreciated that the several embodiments of heat exchangers as described herein may be formed by modifying the manner of operation of the forming apparatus. For instance, the formation of discontinuous channels 21 may be accomplished by selectively moving the cam member 109 away from the split-ring element 102 while the tubing is being moved through the central opening 104 so as to temporarily disengage the angled surfaces 108 from cam-following surfaces 107, thereby eliminating the deforming pressure applied by the rollers 103. Relatedly, the formation along the length of the heat exchanger of offset channels may be accomplished by rotating by a predetermined amount the lengths of tubing 20, 30 within the grip 121 before bringing the angled surfaces 108 of the cam member 109 back into engagement with the cam-following surfaces 107. And relative to the embodiment herein described wherein the channels extend along a helical path, it will be appreciated that such a configuration may be accomplished by rotating the lengths of tubing 20, 30 within the grip 121 simultaneously with both the continued movement of the tubing through the central opening 104 by corresponding movement of the sled 123 and the application of deforming pressure by the press 101 as heretofore described.

It will be understood that, according to the aforedescribed methodology, the formation of a heat exchanger wherein the inner, second length of tubing 30 is formed to include channels 21 will necessitate first forming such channels on the second length of tubing in the forming apparatus 100 and then disposing that length of tubing within the first length of tubing 20; the exemplary forming apparatus 100 as described does not permit disposing the second length of tubing 30 within the first 20, and then forming channels 21 on the second length of tubing 30.

It will be appreciated that the cross-sectional shape of channels 21 may be varied by varying the cross-sectional shape of the rollers 103 employed.

The foregoing description of the exemplary embodiments of the invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the innovation. The embodiments shown and described in order to explain the principals of the innovation and its practical application to enable one skilled in the art to utilize the innovation in various embodiments and with various modifications as are suited to the particular use contemplated. Although only a limited number of embodiments of the present innovations have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible without materially departing from the novel teachings and advantages of the subject matter recited. Accordingly, all such modifications are intended to be included within the scope of the present innovations. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the spirit of the present innovations. 

1. An in-line heat exchanger, comprising: first and second lengths of seamless, walled tubing, the first length of tubing characterized by a larger diameter than the diameter of the second length of tubing, and the second length of walled tubing disposed within the first length of walled tubing; a plurality of longitudinally-extending channels defined in the wall of at least one of the first and second lengths of tubing, the channels defining therebetween a plurality of longitudinally-extending passageways in the area between the walls of the first and second lengths of tubing; and terminal portions provided at opposite ends of the first length of tubing, the terminal portions each sealed with respect to the second length of tubing and each defining one of an inlet or an outlet, and each terminal portion defining at least one interior passageway between the terminal portion and the wall of the second length of tubing, the at least one interior passageway communicating the plurality of longitudinally-extending passageways with one of the inlet or outlet.
 2. The heat exchanger of claim 1, wherein the terminal portions are each defined by opposite ends of the first length of tubing that are sealed against the wall of the second length of tubing.
 3. The heat exchanger of claim 1, wherein the terminal portions comprise separate lengths of tubing that are connected to each of the first and second lengths of tubing.
 4. The heat exchanger of claim 1, wherein the terminal portions have different longitudinal dimensions with respect to each other so as to define interior passageways of different volumes.
 5. The heat exchanger of claim 4, wherein one of the terminal portions defines an interior passageway capable of accommodating an amount of a high-pressure, sub-cooled fluid at least equivalent to the weight of the quantity of a high-pressure fluid that can be accommodated in the receiver dryer in a fully-charged air-conditioning system.
 6. The heat exchanger of claim 1, wherein the plurality of longitudinally-extending channels are defined in the wall of the first length of tubing.
 7. The heat exchanger of claim 1, wherein the plurality of longitudinally-extending channels are defined in the wall of the second length of tubing.
 8. The heat exchanger of claim 1, wherein the plurality of longitudinally-extending channels are defined in the walls of both the first and second lengths of tubing.
 9. The heat exchanger of claim 1, wherein the plurality of longitudinally-extending channels comprise at least two discrete sets of longitudinally-extending channels.
 10. The heat exchanger of claim 9, wherein each discrete set of channels is separated from the other by an intermediate space defined in the area between the walls of the first and second lengths of tubing.
 11. The heat exchanger of claim 9, wherein at least one discrete set of channels is offset relative to the one or more other sets of channels.
 12. The heat exchanger of claim 11, wherein each discrete set of channels is separated from the other by an intermediate space defined in the area between the walls of the first and second lengths of tubing.
 13. The heat exchanger of claim 1, wherein the plurality of longitudinally-extending channels each define a helical path.
 14. A method for forming in-line heat exchangers, comprising the steps of: providing at least first and second lengths of seamless, walled tubing, the first length of tubing characterized by a larger diameter than the diameter of the second length of tubing, and each of the at least first and second lengths of walled tubing characterized by generally circular cross-sectional shapes; inwardly deforming circumferentially spaced-apart portions of the wall of at least one of the first and second lengths of tubing to form along a longitudinal length thereof a plurality of longitudinally-extending channels; and positioning the second length of walled tubing within the first length of walled tubing so that the walls of the first and second lengths of tubing are in contact proximate the plurality of longitudinally-extending channels, and so that, intermediate the areas of contact between the first and second lengths of walled tubing proximate the plurality of longitudinally-extending channels there are defined between the walls of the first and second lengths of tubing a plurality of longitudinally-extending passageways.
 15. The method of claim 14, wherein the step of positioning the second length of walled tubing within the first length of walled tubing is carried out before the step of inwardly deforming circumferentially spaced-apart portions of the wall of at least one of the first and second lengths of tubing.
 16. The method of claim 15, wherein the step of inwardly deforming circumferentially spaced-apart portions of the wall of at least one of the first and second lengths of tubing comprises inwardly deforming circumferentially spaced-apart portions of the wall of the first length of tubing.
 17. The method of claim 14, wherein the step of positioning the second length of walled tubing within the first length of walled tubing is carried out after the step of inwardly deforming circumferentially spaced-apart portions of the wall of at least one of the first and second lengths of tubing.
 18. The method of claim 17, wherein the step of inwardly deforming circumferentially spaced-apart portions of the wall of at least one of the first and second lengths of tubing comprises inwardly deforming circumferentially spaced-apart portions of the wall of the second length of tubing.
 19. The method of claim 17, wherein the step of inwardly deforming circumferentially spaced-apart portions of the wall of at least one of the first and second lengths of tubing comprises inwardly deforming circumferentially spaced-apart portions of the walls of the first and second lengths of tubing.
 20. The method of claim 14, wherein the step of inwardly deforming circumferentially spaced-apart portions of the wall of at least one of the first and second lengths of tubing to form along a longitudinal length thereof a plurality of longitudinally-extending channels further comprises forming those channels intermediate of terminal sections of the first length of tubing, and wherein the method further comprises the step of sealing the ends of the terminal sections against the wall of the second length of tubing to define terminal portions each defining at least one interior passageway between the terminal portion and the wall of the second length of tubing, the at least one interior passageway communicating the plurality of longitudinally-extending passageways, and the step of forming one of an inlet or outlet passageway in each terminal section, the inlet and outlet each communicating one or the other of the at least one interior passageways defined in each terminal portion.
 21. The method of claim 20, wherein the terminal portions have different longitudinal dimensions with respect to each other so as to define interior passageways of different volumes.
 22. The method of claim 21, wherein one of the terminal portions defines an interior passageway capable of accommodating an amount of a high-pressure, sub-cooled fluid at least equivalent to the weight of the quantity of a high-pressure fluid that can be accommodated in the receiver dryer in a fully-charged air-conditioning system.
 23. The method of claim 17, wherein the plurality of longitudinally-extending channels comprise at least two discrete sets of channels, each discrete set of channels comprising a plurality of longitudinally-extending channels.
 24. The method of claim 23, wherein each such discrete set of channels is separated from the other by an intermediate space defined in the area between the walls of the first and second lengths of tubing.
 25. The heat exchanger of claim 23, wherein at least one discrete set of channels is offset relative to the one or more other discrete sets of channels.
 26. The method of claim 25, wherein each such discrete set of channels is separated from the other by an intermediate space defined in the area between the walls of the first and second lengths of tubing.
 27. The heat exchanger of claim 14, wherein the plurality of longitudinally-extending channels each define a helical path.
 28. A method for forming in-line heat exchangers, comprising the ordered steps of: providing at least first and second lengths of seamless, walled tubing, the first length of tubing characterized by a larger diameter than the diameter of the second length of tubing, and each of the at least first and second lengths of walled tubing characterized by generally circular cross-sectional shapes; positioning the second length of walled tubing within the first length of walled tubing; and deforming inwardly circumferentially spaced-apart portions of the wall of the first length of tubing to bring the same into contact with the wall of the second length of tubing, thereby forming along a longitudinal length of the tubing a plurality of longitudinally-extending channels in the wall of the first length of tubing, the plurality of longitudinally-extending channels defining therebetween a plurality of longitudinally-extending passageways between the walls of the first and second lengths of tubing.
 29. The method of claim 28, wherein the step of inwardly deforming circumferentially spaced-apart portions of the wall of the first length of tubing to form along a longitudinal length thereof a plurality of longitudinally-extending channels further comprises forming those channels intermediate of terminal sections of the first length of tubing, and wherein the method further comprises the step of sealing the ends of the terminal sections against the wall of the second length of tubing to define terminal portions each defining at least one interior passageway between the terminal portion and the wall of the second length of tubing, the at least one interior passageway communicating the plurality of longitudinally-extending passageways, and the step of forming one of an inlet or outlet passageway in each terminal section, the inlet and outlet each communicating one or the other of the at least one interior passageways defined in each terminal portion.
 30. The method of claim 29, wherein the terminal portions have different longitudinal dimensions with respect to each other so as to define interior passageways of different volumes.
 31. The method of claim 30, wherein one of the terminal portions defines an interior passageway capable of accommodating an amount of a high-pressure, sub-cooled fluid at least equivalent to the weight of the quantity of a high-pressure fluid that can be accommodated in the receiver dryer in a fully-charged air-conditioning system.
 32. The method of claim 28, wherein the plurality of longitudinally-extending channels comprise at least two discrete sets of channels, each discrete set of channels comprising a plurality of longitudinally-extending channels.
 33. The method of claim 32, wherein each such discrete set of channels separated from the other by a circumferential chamber defined in the area between the walls of the first and second lengths of tubing.
 34. The method of claim 32, wherein at least one discrete set of channels is offset relative to the one or more other discrete sets of channels.
 35. The heat exchanger of claim 28, wherein the plurality of longitudinally-extending channels each define a helical path. 